I'm just a programmer without GIS-skills as such. Hence this question:


  • I have a lot of polygons; actually each private-owned real estate in my country.
  • I also have "counties" as polygons.
  • In each county there are a varying number of (administrative) subdivisions (2 to 55) - and each real estate belongs in one of these subdivisions.
  • But real estates are divided by roads and there are blank areas without any relation to the subdivisions.

My goal is

  • To have just one polygon for each subdivision.
  • Have the blank spaces between real-estate-polygons divided evenly between subdivisions.
  • The county marks the outer border.

Simple example:

enter image description here

All the red boxes are merged. All the green are merged. The spaces between are shared. The black box is the outer limit.

Is there a readily available tool that can do this easily? Like QGis, ArcGIS, a db-engine or library/API? I've tried perusing the different options, I've tried testing various approaches, but to no avail.

If there aren't any tools, I guess I need to program it myself. Any thoughts?

If there is a term describing the process above, please let me know: I'm such a GIS-noob, so I don't even know what to Google :-)

  • This is something you can do by invoking different libraries. You can do this using your programming skill in python or other languages. You can also do this using a user interface in say QGIS or other tools. An answer should take the two different approaches into account. – ragnvald Mar 9 '15 at 21:12
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    You could have a look at using voronoi polygons as one way forward. They generally are done around points, but you could use the polygon vertices to build them, then categorise the polygons based on the point inside them. – MickyT Mar 9 '15 at 21:52
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    Voronoi is the way I'd go for vector. For raster I'd use Euclidean Allocation (that's an Esri tool). Filling by Voronoi/Thiessen en.wikipedia.org/wiki/Voronoi_diagram would do the job but it can get a little hazy outside the sample area (look at the picture on the link). QGIS has a good API qgis.org/api/annotated.html and it's free, Esri has an AWESOME API (in fact so awesome it's very hard to find where to start) but it's definitely not free. – Michael Stimson Mar 9 '15 at 22:06
  • Already tried the Voronoi-approach: it didn't create the result, I wanted. But some variation on Voronoi using line-segments might do the trick – it sounds right... The Euclidean Allocation approach might be the easiest however: buy some ESRI-tool, convert my shapes to raster, run the Euclidian Allocation on the raster, convert the raster to vector, clean up and voilà. I guess? – Jens Mar 10 '15 at 10:33
  • FYI: this approach in QGis works - but only in very simple scenarios: Dissolve polygons, densify polygons, extract nodes, voronoi, dissolve, simplify. Not good enough for real-life maps though - lines too jagged. – Jens Mar 12 '15 at 13:52

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